The need for determining the freeze point of antifreeze-containing solutions is well established. Perhaps this type of determination is most commonly employed in checking the freeze resistance of automobile engine cooling systems. While this type of determination is relatively common in colder climates, the advent of high compression engines and automobile air conditioners has resulted in the addition of antifreeze to automobile cooling systems in all climates. This is now a standard procedure because antifreeze not only lowers the freezing point of the cooling system solution, it also raises the boiling point of the solution.
The commonly employed method of determining freeze points of antifreeze-containing solutions is to remove a sample of the solution and determine the specific gravity thereof by use of a hydrometer, a floating ball device or the like. In most instances, the readings of the hydrometer are correlated to freeze points because the concentration of the solution, measured by specific gravity, is usually directly proportional to the freeze point thereof. In the case of the floating ball device a number of balls are employed, each ball having a different density. The balls that sink in the solution, due to the weight of the balls and the concentration of the antifreeze in the solution, are determinative of the specific gravity of the solution. Due to the relatively large amount of sample necessary to conduct these tests, the sample is usually replaced in the container, i.e. the radiator from which the test solution was obtained, at the end of each test.
Common to each of the hereinbefore described commonly used methods is a mechanical instrument adapted to detect a property of the antifreeze-containing solution; namely the change in the specific gravity of the solution upon a variation of the concentration of antifreeze in the solution.
The mechanical instrument used with the previously described methods inherently provides the following disadvantages: it is subject to breakage and is relatively expensive, the floats thereof can become dirty and difficult to read, and a relatively large amount of sample solution is required to lift the float.